Smart cards are widely used in people's daily lives. At present, smart cards, such as bus cards, bank cards, and the like, are generally magnetic cards or radio-frequency (“RF”) integrated-circuit (“IC”) cards. In existing cards, information carried by the cards can be easily copied or lost. Existing methods and designs for protecting data, however, have issues. For example, RF communications are greatly affected by metal casings, metal cannot be inlaid in a card, and high-end gold cards cannot be produced. Furthermore, both magnetic cards and RF IC cards need special card-reading devices to read data therefrom or write data thereto. Therefore, the existing smart cards need to be further improved.